Many remote accessory devices are designed to be powered by mobile direct current (DC) sources such as storage batteries and related systems used in automobiles, pleasure boats, etc. Due to the idiosyncrasies of portable power supplies, devices such as cellular phones or notebook computers require cable connections and power converters specifically designed to interface with mobile power supplies such as a cigarette lighter power source commonly found in cars and other vehicles.
Generally, portability is greatly desired and expected in many devices used either in a vehicle or at home. For example, a cellular phone may preferably be used at home or in the car because it typically incurs service charges similar to that of telephones hardwired in a house. Furthermore, to limit the necessity of keeping track of multiple phone numbers or the associated expenses, users typically prefer to utilize a single mobile phone unit wherever a suitable power source is located. Such use limits phone expenses by limiting the number of individual phone units to typically one cellular unit. Therefore, household voltage power converters and adapters have been created for allowing a greater variety of locations in which low voltage devices such as cellular phones can be used.
When exposed to the overloads typical in household AC power supplies, either the converter or the portable device may suffer damage requiring repair expense and inconvenience. A need exists for conversion circuitry that latches into an inoperative state while the overload condition persists.